RStudio Desktop

• RStudio Desktop is a free-integrated development environment (IDE) for R.
• It incorporates:
  • A Console pane to execute instructions interactively.
  • An Environment pane to control existing variables.
  • An R script editor. Supporting other languages: html, css, markdown, python, C/C++, …
• RStudio is becoming Posit https://posit.co/.
• RStudio Desktop can be downloaded at https://rstudio.com/products/rstudio/download/.

Vectors: atomic’s and list’s

• Atomic vectors
  • logical,
  • integer,
  • numeric,
  • character, and also
  • raw and complex.
  • Coercing order: logical \(\rightarrow\) integer \(\rightarrow\) numeric \(\rightarrow\) character
• Lists

Atomic vectors (1)

• Four most common types:

v_num = c(2,4,3,5,4,6,6)
v_num
v_char = c('Vector', 'of', 'strings')
v_char
v_int = c(2L,4L,3L,5L,4L,6L,6L)
v_int
v_log = c(TRUE, FALSE, FALSE, TRUE, FALSE)
v_log

• Coercing order:

v_mixed = c("Vector", "with", 1, "number")
v_mixed
typeof(v_mixed)
# more coercions
c(TRUE, 1L, 1, "one")
c(TRUE, FALSE, 2, 4)

• To assign, we can use <- (most common) o -> operators (least common):

a1 <- c(1,2,3)
c(1,2,3) -> a2

Atomic vectors (2)

• Building atomic vectors

0:20
seq(0,20,2)
seq(20,0,-2)
seq(0, 20, length=20)
sample(0:20)
scan("https://raw.githubusercontent.com/srmalins/primelists/master/100000primes/primes.0000", nmax = 10)
scan(text = "0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144", sep = ',')
scan(text = "Building atomic vectors", what = character())

• Constants

LETTERS
letters
month.name
month.abb
pi

Atomic vectors (3)

• NA is a symbol to define a non-available observation.
• We can operate with NA:

NA + 3
NA ^ 0
NA | FALSE
NA | TRUE
mean( c(1, 3, 2, NA) )
mean( c(1, 3, 2, NA), na.rm = TRUE )

• We can ask if an element is NA or if a vector has some NA:

is.na( c(1, 3, 2, NA) )
anyNA( c(1, 3, 2, NA))

Lists

• Lists can be created using function list():

my_list = list(
  c("first", "element"),
  c(TRUE, FALSE, TRUE),
  list(),
  1:20
)
my_list

• A particular type of list is the data.frame, where elements should have the same length:

my_data = data.frame(
  name = c('Marc', 'Manel', 'Christine', 'Sonia'),
  sex = c('male', 'male', 'female', 'female'),
  age = c(40, 45, 30, 43) )
my_data
# my_data is a list
is.list(my_data)

Selecting vectors (1)

• Positive integers

month.abb[c(1,3,5,7,9,11)]

• Negative integers

month.abb[c(-1,-3,-5,-7,-9,-11)]

• Logical vectors

month.abb[c(T,F,T,F,T,F,T,F,T,F,T,F)]

• Vector of names (only with named vectors)

x = 1:12
names(x) = month.abb
x[c("Jan", "Mar", "May", "Jul", "Sep", "Nov")]

Selecting vectors (2)

• Selection is valid for lists

my_list[c(1,1,3)]
my_list[-3]
my_list[c(T,F,F,T)]
my_data[c('name', 'age')]

• Only for list’s: we use [[]] to obtain the content of one vector’s element.

my_list[[1]]
my_data[['age']]
# equivalently, for named list, we can use $
my_data$age

• Only for data.frame’s: we use [rows,columns] to slice a table by rows and columns.

my_data[c(1,3), c(1,3)]
my_data[c(TRUE, FALSE, TRUE, FALSE),]
my_data[,1:2]
my_data[,1]            # equivalent to my_data[[1]]
my_data[,1,drop=FALSE] # equivalent to my_data[1]

Activity

• Suppose queue = c("Maria", "Josep", "Marçal", "Lluïsa") represents a supermarket queue, with Maria first in line. Using R expressions update the supermarket queue:
  1. Manel arrives;
  2. Maria is served;
  3. Vicens talks her way to the front with one item;
  4. Manel gets impatient and leaves;
  5. Marçal gets impatient and leaves;

Functions

Structure:

function(...){
  ...
  # Some code
  ...
  return(some_result)
}

It is common to avoid the return() statement:

function(...){
  ...
  # Some code
  ...
  some_result
}

Functions

Fibonacci numbers \(F_0, F_1, F_2, \dots\) can be defined recursively as

\[ F_n = \left\{\begin{matrix} n & \text{si $0 \leq n \leq 1$} \\ F_{n-1} + F_{n-2} & \text{si $2 \leq n$} \end{matrix}\right. \]

Recursive implementation:

Fn_rec = function(n){
  if(n < 0 | n != round(n)) stop("n must be a non-negative integer", call. = FALSE)
  if(n <= 1) return(n)
  Recall(n-1) + Recall(n-2)
}

Iterative implementation:

Fn_ite = function(n){
  if(n < 0 | n != round(n)) stop("n must be a non-negative integer", call. = FALSE)
  if(n <= 1) return(n)
  Fn_v = rep(0, n)
  Fn_v[1:2] = 1
  for(i in 3:n){
    Fn_v[i] = Fn_v[i-1] + Fn_v[i-2] 
  }
  Fn_v[n]
}